The aim of this project is to assess the relationship between the child outcomes of developmental disability and mental retardation (DD/MR) and maternal exposure to chemicals in soil during each month of pregnancy. This is the second phase in our investigation that builds on our findings of suspect inorganic chemicals (As and Cr) and improved statistical methods to conduct analyses of spatial relationships. In the second phase we will continue to test our hypotheses about clusters and suspect chemical exposures in South Carolina. Hypothesis 1: There are at least four additional clusters of DD/MR among infants identified by maternal residence during pregnancy. (Confirm phase 1 findings); Hypothesis 2: There are statistically significant associations between As, Cr, Pb, Hg, and pesticide exposures during critical periods of fetal development and risk for DD/MR in the infant, after controlling for maternal and child risk factors. (Confirm phase 1 findings) We will add two new components to develop statistical methods to analyze complex residential histories as they impact the outcome and to identify threshold levels of chemical concentrations that are predictive of excess risk for DD/MR. Hypothesis 3: At an individual level of analysis cumulative exposure to suspect chemicals from different residential exposures will be associated with the outcome. (NEW); and Hypothesis 4: For each of the chemicals associated with the outcome there will be a soil threshold that is associated with statistically elevated risk. (NEW) The study will be divided into three steps: (1) Identify suspect chemicals associated with DD/MR based on month of exposure. (2) Develop methods to utilize address change information and the entry and exit of individuals into the cohort, during the months of pregnancy in our modeling. (3) Develop methods to minimize the measurement error in the analysis of large data sets with both large number of observations and large number of variables. This research will provide epidemiologic evidence for an association of suspect chemicals and DD/MR and statistical innovation to analyze these associations that take into account measurement error, large spatial sample size, and other statistical challenges. PUBLIC HEALTH RELEVANCE: The aim of this project is to assess the relationship between the child outcomes of developmental disability and mental retardation (DD/MR) and maternal exposure to chemicals in soil during each month of pregnancy. The importance of this research is substantial in terms of improved environmental spatial analysis and public health implications.